Assessing the presence of microplastic particles in Tunisian agriculture soils and their potential toxicity effects using Eisenia andrei as bioindicator

In the present study, we investigated microplastics (MPs) in agricultural soils with different agronomic practices (organic farming, soil under greenhouses, soil under mulching and soil irrigated with treated wastewater (TWW)). Plastic particles from each site were collected and characterized by FTIR and Raman microspectroscopy. Plastic particles were then ground and added (size rage under 100 mu m) at a concentration of 100 mu g kg(-1) to soils from organic farming containing Eisenia andrei for 7 and 14 days. MPs accumulation in earthworms was quanti-fied and characterized. Oxidative stress was assessed by evaluating the activities of catalase, glutathione-S-trans-ferase, and acetylcholinesterase as well as malondialdehyde accumulation. Our results revealed higher quantity of MPs in soils ranging from 13.21 +/- 0.89 to 852.24 +/- 124.2 items kg(-1) with the dominance of small sizes (0.22-1.22 mu m). Polyethylene (PE) and polybutyrate adipate terephtalate (PBAT) were the dominant MPs. More-over, our results revealed a significant ingestion of MPs in earthworms with values ranging from 1.13 to 35.6, characterized mostly by PE, PBAT and polypropylene (PP). Biochemical data revealed an important alteration in worms exposed to MPs from soils with mulching and irrigated with TWW. Our study provides new insights into the effects of microplastic in earthworms and thus the vulnerability of terrestrial ecosystem to this emergent contaminant. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study revealed a high quantity of microplastics in agricultural soils, dominated by small sizes of polyethylene and polybutyrate adipate terephtalate. Earthworms ingested a significant amount of microplastics, leading to important biochemical alterations.